Resin matrix composites such as carbon fiber-reinforced epoxy resin composites and glass fiber-reinforced polyester resin composites are useful in applications where a high strength and stiffness to weight ratio are required. However, the composites exhibit poor fire resistance because of their high degree of flammability, rapid flame spread, high rate of heat release and, in some cases, production of toxic combustion gases. Many solutions have been proposed for improving the fire resistance of composites and other heat-sensitive substrates, for example, addition of halogenated materials to the resin; addition of aluminum trihydrate, borate salts or polyammonium phosphates to the resin; application of intumescent coatings to the substrate; and use of thick inorganic fiber mats as insulation. All of these materials have disadvantages, however, such as generation of toxic and corrosive halogenated gases, deterioration in the physical properties of the substrate, the necessity for several time-consuming and labor intensive coating applications, and low abrasion resistance of the protective material.
Vermiculite in various forms has been used for fire protection of heat-sensitive substrates. For example, U.S. Pat. Nos. 4,442,164 and 4,543,287 disclose the use of a composite of fibers coated with chemically delaminated vermiculite for the fire protection of substrates. U.S. Pat. No. 4,888,233 discloses coating a substrate with a composition comprising chemically delaminated vermiculite and a copolymer of ethylene and a vinyl monomer to impart fire and heat resistance. U.S. Pat. No. 4,678,700 discloses the use of carbon fibers coated with chemically delaminated vermiculite to insulate substrates and protect them from fire.